1. Field of the Invention
The present invention relates generally to an electron emission device, and more particularly to an electron emission display device which has a plurality of electron emission devices arranged in an image display array, for example, in a matrix form.
2. Description of the Related Art
Conventionally, in field electron emission display apparatuses, a Field Emission Display (FED) is known as a planar emission display device equipped with an array of cold cathode electron emission sources which does not require cathode heating. The emission principle of, for example, an FED using Spindt-type cold cathodes of minute protrusions is as follows: Its emission principle is like a Cathode Ray Tube (CRT), although this FED has a cathode array of Spindt-type protrusions which is different from that of CRT. In the FED, electrons are drawn into a vacuum space by means of each gate electrode spaced apart from the Spindt-type cathode, and the electrons are made to impinge upon the fluorescent substance that is coated on a transparent anode, thereby causing light emission.
This FED, however, has a problem of low production yield because the manufacture of the minute Spindt-type emitter arrays as a cold cathode is complex and involves many processes.
There is also known an electron emission device with electron emission devices of metal-insulator-metal (MIM) structure as a planar electron emission source. The electron emission device with the MIM structure comprises an Al underlayer as a base electrode, an Al2O3 insulator layer with about 10 nm thickness, and an Au overlayer, as a top electrode with about 10 nm thickness which are formed in order on the substrate. In the case that this MIM device is placed under an opposing electrode in a vacuum, when a voltage is applied between the Al underlayer and the Au overlayer and, at the same time, an acceleration voltage is applied to the opposing electrode, then some of electrons emit out of the Au overlayer and reach the opposing electrode. In this device, electrons are also made to impinge upon the fluorescent substance coated on the opposing electrode, thereby causing light emission.
These light emitting devices of FED type require a vacuum space in which emitted electrons travel while accelerated towards fluorescent materials and an electric circuit for accelerating the emitted electrons, resulting in an enlarged structure as a whole for a display apparatus.
The present invention has been made in view of the above circumstances, and thus an object thereof is to provide an electron emission light emitting device having a simple structure capable of stably emitting light and electrons at a low voltage applied thereto, and moreover a display apparatus including a flat panel display device which employs a plurality of such electron emission light-emitting devices.
The present invention provides an electron emission light-emitting device which comprises:
an electron emission device including an electron-supply layer made of semiconductor formed on an ohmic electrode, an insulator layer formed on the electron-supply layer, and a thin-film metal electrode formed on the insulator layer, whereby the electron emission device emits electrons when an electric field is applied between the electron-supply layer and the thin-film metal; and
a fluorescent material layer formed on said thin-film metal.
According to the electron emission light-emitting device having the structure mentioned above, said insulator layer is made of dielectric and has a film thickness of 50 nm or greater.
The present invention further provides an electron emission display device which comprises:
a back substrate; and
a plurality of electron emission light-emitting devices formed on said back substrate each comprising;
an electron emission device including an electron-supply layer made of semiconductor formed on an ohmic electrode, an insulator layer formed on the electron-supply layer, and a thin-film metal electrode formed on the insulator layer, whereby the electron emission device emits electrons when an electric field is applied between the electron-supply layer and the thin-film metal; and
a fluorescent material layer formed on said thin-film metal.
In the electron emission display device according to the invention, said insulator layer is made of dielectric and has a film thickness of 50 nm or greater.
The electron emission display device according to the invention further comprises an optically transparent front substrate opposing to said back substrate and sandwiching said electron emission light-emitting devices and the fluorescent material layer.
The electron emission display device according to the invention further comprises a collector electrode formed on an inner surface of said front substrate.
In the electron emission display device according to the invention, the display device further comprises a plurality of bus electrodes, each of which is arranged in a stripe form to electrically connect adjacent ones of said thin-film metal electrodes, wherein said ohmic electrodes and said electrodes are stripe-like electrodes and arranged to extend perpendicular to each other.
In the electron emission display device according to the invention, the display device further comprises plural insulative support members formed on said back substrate and disposed between adjacent ones of said electron emission devices so as to enclose the electron emission devices for partitioning them, wherein the distance from said back substrate to the surfaces of said insulative support members is substantially equal to the distance from said back substrate to the surface of said thin-film metal electrodes proximate to said vacuum space.
According to the electron emission light-emitting device of the invention with the above structure, since the fluorescent material layer is formed on the thin-film metal electrode of the electron emission device, no extra electric power is required for accelerating electrons, so that the simple driving circuit may be used in the display device. Further since there is no vacuum space between the fluorescent material layer and the thin-film metal electrode, a super thin flat panel display device is obtained by utilizing the electron emission light-emitting device of the invention and such a panel display device has a good view from outside since there is no necessity of extra spacer for a vacuum space.
Moreover, through-bores are not likely to be produced in the insulator layer because of its relatively thick thickness and therefore its production yield is improved. The electron emission light-emitting device of the invention is a planar or spot-like electron emission diode and can be adapted to high speed devices such as a source of a pixel vacuum tube or bulb, an electron emission source of a scanning or transmission electron microscope, a vacuum-micro electronics device and the like. In addition, this electron emission light-emitting device can serve as a minute microwave tube or a diode which emits electromagnetic waves with millimeter or sub-millimeter wavelength, and also can serve as a high speed switching device.